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NEW APPROACH OF DESIGNING AND EXPLOATATION OF ELECTRICAL TRACTION SUBSTATIONS

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Electric traction system
Electric traction system
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NEW APPROACH OF DESIGNING AND EXPLOATATION OF ELECTRICAL TRACTION SUBSTATIONS

  1. 1. 1. Connection of electric traction substations on the principle of input-output 2. Electric traction substation connected to the nearby electric power plant
  2. 2. Connection of electric traction on the principle of input-output with two transmission feeders equipped with three-poles switches, three-phase busbar disconnectors and a three-pole disconnectors with earthing blades
  3. 3. Electric traction substation connected to the nearby electric power plant
  4. 4. There are two transformers, two transmission feeders, the two bus feeders (high voltage and low voltage), two transformer feeders. Each transformer has its own voltage regulator. Each feeder is fitted in same way. The number of redundant paths, redundant equipment and devices is a basic feature of this concept and schemes shown at figures 1 and 2. A variety of spare delivery paths (which would be used in the case of virtually unimaginable coincidences failures of the left feeder, right switch and transformer left) and lots of devices make electric traction substations very complicated.
  5. 5. The solution of this problem is illustrated by applying auxiliary bus
  6. 6. Saving three measuring transformers of 110 kV (decrease the total cost, including installation, footages and required space). The result: more reliable and simpler substation
  7. 7. Based on long time researching and studies, as well as broad international survey conducted by the Committee A 50 Office for Research and testing (Office de Recherrches et d'Essais), International Union of Railways, in singlephase substations, surge arresters are not applied anymore. This method of protection when the electric traction substation was built near already protected buses of a power plant is assessed as dangerous for operational reliability and plant staff and removed from the substations in developed countries
  8. 8. The result: transfersally feeders are not necessary on the 110 kV side . Scheme of electric traction substations connected via a three-phase transmission line Transformers that are shown in the picture are without voltage regulators, which are weak spots subjected to failures. Result: increased plant reliability.
  9. 9. The next step of substation simplification is transformer feeder 110 kV and 25 kV feeder lacks and giving to circuit breaker in 110 kV feeder functions of protection of transformer , as it shown in the previous figure. In this case energy measurement is in 25 kV because there are required current and voltage transformers for the protection. So it is necessary to add kWh meters for measuring losses.
  10. 10. -using drawable circuit breakers in 25 kV feeders instead circuit breakers and disconnectors which are elements of wrong manipulations; - the application of switch-disconnectors instead circuit breakers in 25 kV transformer feeders; -aplication of combined instrument transformers (CT and VT in one element) in all feeders;
  11. 11. Bypassing neutral section in separating substations with neutral section and designing electeric traction substations with single transformer - parallel connection of electric traction substations
  12. 12. Thyristor voltage adjustor is required to make identical voltages in catenary in this case.
  13. 13. Distance between electric traction substations increase from 40 - 50 km to 80 - 90 km. Peak power reduction wherein speed of trains do not decrease.
  14. 14. There are necessity for selectivity and accuracy of catenary distant relays with power direction relay in separating substations, because two substations deliver power to electric vehicle and ground fault.
  15. 15. Selectivity of catenary distant relays is acquired with time grading in three zone toward sources.
  16. 16. Equivalent circuit of electric traction system 25 kV; 50 Hz for parallel connected electric traction substations Short circuit current: 𝑰 𝑲𝑺 = 𝑼 𝟐 ∙ 𝒁 𝑴 + 𝒁 𝑻 + 𝒁 𝒆𝒌𝒗 ′ ∙ 𝒍 𝑨 𝒁 𝑴 - impedance of electric network operator for two pole short circuit on 𝟏𝟏𝟎 𝒌𝑽 busbars in electric traction substation reduced on catenary voltage, 𝒁 𝑻 - impedance of single phase transformer of electric traction substations, 𝒁 𝒆𝒌𝒗 ′ - equivalent impedance per unit of length of catenary
  17. 17. 𝒁 𝑴 = 𝒋 ∙ 𝟏,𝟎𝟓∙𝑼 𝟐 𝑺 𝒌 𝜴 U–voltage of catenary 𝑽 , 𝑺 𝒌 – two phase fault power on electric traction substation busbar 𝑽𝑨 𝒁 𝑻 = 𝒋 ∙ 𝒖 𝒌(%) 𝟏𝟎𝟎 𝑼 𝟐 𝑺 𝑻 𝜴 , where: 𝒖 𝒌(%) – relative short circuit voltage % , 𝑺 𝑻 – nominal power of transformer 𝑽𝑨 𝒁 𝒆𝒌𝒗 ′ = 𝒁 𝒗 ′ − 𝜺𝒁 𝒎 ′ + 𝟏−𝒆−𝒌∙𝒍 𝒌∙𝒍 𝟏 − 𝜺 𝟐 𝒁Š𝑰 ′ 𝜴 𝒌𝒎
  18. 18. Carson-Pollaczek formulaes: 𝒁 𝒆𝒌𝒗 ′ = 𝒁 𝒗 ′ − 𝜺𝒁 𝒎 ′ + 𝟏 − 𝒆−𝒌∙𝒍 𝒌 ∙ 𝒍 𝟏 − 𝜺 𝟐 𝒁Š𝑰 ′ 𝜴 𝒌𝒎 𝒁 𝑽 ′ – impedance per unit of length of catenary 𝜴 𝒌𝒎 , 𝒁Š𝑰 ′ –impedance per unit of length of returning current circuit 𝜴 𝒌𝒎 , 𝒍 – distance to electrica traction substation 𝒌𝒎 , 𝒁 𝒎 ′ – mutual impedance per unit of length catenary- returning current circuit 𝜴 𝒌𝒎 , 𝜺 = 𝒁 𝒎 ′ 𝒁Š𝑰 ′ , where: 𝒌 = 𝒁Š𝑰 ′ ∙ 𝒈 𝒌𝒎−𝟏 - propagation coefficient of gauge 𝒈- admittance per unit of length of gauge 𝑺 𝒌𝒎
  19. 19. Impedance per unit of length of returning current circuit with two rails: 𝒁Š𝑰 ′ = 𝟎, 𝟓 𝒓Š𝒂 + 𝒋 𝒙′ + 𝒙′′ + 𝝎𝑴 𝟏,𝟐 ′ 𝜴 𝒌𝒎 , where: 𝒓Š𝒂 –resistance of rails 𝜴 𝒌𝒎 , 𝒙′ - interior reactance per unit of length of rail otpor 𝜴 𝒌𝒎 , 𝒙′′ - external rail reactance per unit of length 𝜴 𝒌𝒎 , 𝝎 = 𝟐𝝅𝒇 𝒔−𝟏 - circle frequency Internal reactance pwr unit of length of S-49 rail: 𝒙′ = 𝟎, 𝟕𝟓 ∙ 𝒓Š𝒂 External rail reactance per unit of length: 𝒋𝒙′′ = 𝟎, 𝟎𝟒𝟗𝟑 − 𝒋𝟎, 𝟏𝟒𝟒𝟔 𝟏, 𝟓𝟑 + 𝒍𝒐𝒈 𝑹Š 𝟐 ∙ 𝜸 𝜴 𝒌𝒎 𝑹Š - radius of equivalent conductor: 𝑹Š = 𝑷 𝟐𝝅 𝒄𝒎 , where P is rail perimeter 𝒄𝒎 . Mutual rails impedance per unit of length: 𝒋𝝎𝑴 𝟏,𝟐 ′ = 𝟎, 𝟎𝟒𝟗𝟑 − 𝒋𝟎, 𝟏𝟒𝟒𝟔 𝟏, 𝟓𝟑 +
  20. 20. Dependance of catenary impedance per unit of length on distance for S-49 and UIC 60 rails
  21. 21. Dependance of catenary impedance arguments on distance for S-49 and UIC 60 rails
  22. 22. Short circuit current of a single truck Overall short circuit current on place of fault is addition of currents from two electrical traction substations.
  23. 23. Dependance of impedance on distance measured by distant relay
  24. 24. Short circuit impedance measured by impedance relays in separating substations (R-X diagram)
  25. 25. CONCLUSION The existing designs of electric traction substations in exploitation proved to be expensive, overcomplicated and unnecessary. Consequences are too large costs of construction and maintenance, overcomplicated facilities, lack of diagrams clearness and problems during maintenance. In this paper, we proposed new ways of substations designing and changes in designs of exploited substations when the reconstruction is needed. It reduces costs, economizes controlling, makes maintenance simplified and improves clearness of electrical traction substations. Availability and safety of substations remains high. Parallel connected traction substations could reduce peak power costs and measurements of energy consumption are simpler. This paper provides electrical calculations for protective relay adjustments in traction systems. Calculations of impedances and short circuit currents are performed using the Wolfram Mathematica program.

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